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Cholinergic and dopaminergic alterations in the mouse central nervous system following acute trimethyltin exposure.

Male mice were given a single oral dose of 0, 1 or 3 mg/kg TMT-hydroxide and sacrificed 48 hrs, 1 and 2 weeks later. Brain areas were removed, dissected and frozen for later analysis of neurotransmitter receptor binding by filtration techniques and determination of concentrations of monoamines and their metabolites by HPLC/EC. Muscarinic cholinergic receptor binding was measured over a [3H]-quinuclidinyl benzilate (QNB) concentration range of 0.02 to 2.0 nM. Two days after TMT treatment, affinity of [3H]-QNB binding in frontal cortex increased. Gradual return to control binding affinity was seen over the next 2 weeks. The number of receptors decreased only at high dose after 1 week. In hippocampus, a similar increase was seen only at the 3 mg/kg dose after 1 and 2 weeks. Homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were significantly decreased in the caudate nucleus 2 weeks after TMT treatment; concentrations of serotonin (5-HT), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC) were unaltered, nor was there a change in dopamine receptors as measured by [3H]-spiroperidol binding in the caudate nucleus or frontal cortex. To determine if TMT altered monoamine turnover or metabolite efflux, mice were dosed with 0 or 3 mg/kg TMT; 2 weeks later, pargyline (75 mg/kg, intraperitoneally) was administered and the mice sacrificed 0, 30 and 60 min. later. Monoamines and their metabolites were measured in caudate nucleus. The HVA elimination rate was unchanged. The data suggests that the lower concentrations of dopamine metabolites observed 2 weeks after TMT treatment were due to a decrease in dopamine turnover. The decrease in muscarinic receptor affinity in frontal cortex and hippocampus and the decrease in the rate of dopamine turnover in the caudate nucleus indicate that these 2 systems are affected by TMT and may participate in the expression of its toxicity.

Animals↗

Increased methylation of chloroform extractable products and CTP: cholinephosphate cytidylyltransferase in brain membrane preparations from triethyltin-intoxicated rats.

Rats were chronically intoxicated with triethyltin in the drinking water (0.002%) for a period of 15 days. Starting with day 5 of the intoxication period a decrease in the body weight was observed and, in parallel, the development of a cerebral oedema could be followed by measuring white matter density. At the same time, an increase of phosphatidylethanolamine-N-methyltransferase and cholinephosphate cytidylyltransferase activities was noted. This increase might be a compensatory mechanism for counteracting the membrane damages induced by triethyltin.

Animals↗

Tri-n-butyltin increases intracellular Ca2+ in mouse thymocytes: a flow-cytometric study using fluorescent dyes for membrane potential and intracellular Ca2+.

Effects of tri-n-butyltin (TBT) on mouse thymocytes were examined using a flow-cytometer and fluorescent dyes for membrane potential and intracellular Ca2+ ([Ca2+]i). TBT at concentrations from 1 x 10(-7) M to 3 x 10(-7) M caused hyperpolarization in thymocytes during 30 min. after drug application in a time- and dose-dependent manner. Further increase in TBT concentration (to 1 x 10(-6) M) made hyperpolarization of thymocytes more profound within 5 min. after application, thereafter gradually depolarized them during the next 25 min. TBT at 3 x 10(-8) M or more (up to 1 x 10(-6) M) increased the [Ca2+]i of thymocytes. After reaching maximum [Ca2+]i at the various TBT concentrations used within 5 min. after drug application, the [Ca2+]i slightly decreased in a time-dependent manner. Effects of TBT on membrane potential and the [Ca2+]i were greatly reduced under nominal external Ca(2+)-free condition. Results suggest that TBT can promote Ca(2+)-influx to thymocytes, resulting in hyperpolarization by activation of Ca(2+)-dependent K+ current. The increase in [Ca2+]i by TBT may be related to its cytotoxic action on thymocytes.

Animals↗

Effects of concurrent exposure to tributyltin and 1,1-dichloro-2,2 bis (p-chlorophenyl) ethylene (p,p'-DDE) on immature male Wistar rats.

Tributyltin and 1, 1-dichloro-2, 2 bis (p-chlorophenyl) ethylene (p,p'-DDE) have been ubiquitously distributed over the world. In Japan, p,p'-DDE and tributyltin are ingested through marine products, in which these substances are accumulated through bio-concentration and the food chain. However, the consequence of potential combined hazards of these substances remains unknown. Therefore, the effects of concurrent exposure to 125 ppm p,p'-DDE and 25 ppm tributyltin were investigated in immature male Wistar rats by oral administration during puberty. In this study, tributyltin promoted the growth of pubertal male rats, while p,p'-DDE itself did not affect the growth but inhibited the growth enhancement by tributyltin. Furthermore, tributyltin reduced thymus weight but p,p'-DDE also prevented this weight reduction. Neither development of male sexual accessory organs nor sexual maturation was affected even by concurrent exposure to p,p'-DDE and tributyltin. No significant changes of serum testosterone, luteinizing hormone, follicle-stimulating hormone concentrations, and epididymal sperm numbers were observed with the administration of p,p'-DDE and/or tributyltin. These results indicate that sexual maturation, male reproductive organ development and sperm production is scarcely affected in immature male Wistar rats even by concurrent exposure to p,p'-DDE and tributyltin at a daily dose of ca. 2 mg/kg tributyltin and 10 mg/kg p,p'-DDE. Moreover, the simultaneous administration of p,p'-DDE with tributyltin counterbalanced the effects that were attributed to tributyltin alone.

Animals↗

Bacteriostatic and bactericidal modes of action of bis(tributyltin)oxide on Legionella pneumophila.

The modes of action of bis(tributyltin)oxide (TBTO) doses between 1 X 10(4) and 6 X 10(7) molecules per cell on a single environmental isolate of Legionella pneumophila were studied by monitoring the following parameters: (i) growth, (ii) cell viability, (iii) 14C-amino acid incorporation, (iv) 14CO2 production from 14C-amino acids, (v) [3H]uridine incorporation, (vi) [3H]thymidine incorporation, (vii) oxygen consumption, (viii) cellular ATP levels, and (ix) adenylate energy charge. The amount of TBTO associated with the cells in these laboratory cultures was also compared with that remaining in the suspending medium. Most of the TBTO (68 to 88%) was found to be associated with the cells. This result explained why the cellular responses which were measured did not correlate with the TBTO concentration, but rather with the dose of TBTO to which the cells were exposed. At the lower TBTO doses tested (10(4) to 10(7) molecules per cell) a log-normal relationship was observed between the reduction in growth rate and the TBTO concentration. At intermediate TBTO doses (ca. 10(7) molecules per cell) growth stasis occurred, with nearly 100% of the cells in these cultures remaining viable for at least 5 h after treatment. The cellular function which seemed to be primarily affected at these levels of TBTO was the energy conversion mechanism, since the decline in the rates of CO2 production, oxygen consumption, and macromolecular synthesis was preceded by an immediate (within 1 min) drop in the intracellular levels of ATP and the adenylate energy charge. At the higher TBTO doses greater than 10(7) molecules per cell) an initial, precipitous, drop in the number of viable cells was observed, which was followed by a further exponential reduction of viable cells in the treated culture. This dramatic increase in bactericidal activity with a slight increase in the TBTO dose indicated that the modes of bacteriostatic and bactericidal action of TBTO were different.

Adenine Nucleotides↗

Tributyltin-resistant bacteria from estuarine and freshwater sediments.

Resistance to tributyltin (TBT) was examined in populations from TBT-polluted sediments and nonpolluted sediments from an estuary and from fresh water as well as in pure cultures isolated from those sediments. The 50% effective concentrations (EC50s) for populations were higher at a TBT-polluted freshwater site than at a site without TBT, suggesting that TBT selected for a TBT-resistant population. In contrast, EC50s were significantly lower for populations from a TBT-contaminated estuarine site than for those from a site without TBT, suggesting that other factors in addition to TBT determine whether populations become resistant. EC50s for populations from TBT-contaminated freshwater sediments were nearly 30 times higher than those for populations from TBT-contaminated estuarine sediments. We defined a TBT-resistant bacterium as one which grows on trypticase soy agar containing 8.4 microM TBT, a concentration which prevented the growth of 90% of the culturable bacteria from these sediments. The toxicity of TBT in laboratory media was influenced markedly by the composition of the medium and whether it was liquid or solid. Ten TBT-resistant isolates from estuarine sediments and 19 from freshwater sediments were identified to the genus level. Two isolates, each a Bacillus sp., may be the first gram-positive bacteria isolated from fresh water in the presence of a high concentration of TBT. There was a high incidence of resistance to heavy metals: metal resistance indices were 0.76 for estuarine isolates and 0.68 for freshwater isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

Copper↗

Occurrence of tributyltin-tolerant bacteria in tributyltin- or cadmium-containing seawater.

Tributyltin chloride (TBTCl)-tolerant bacteria accounted for 90% of the flora in natural seawater to which TBTCl was added. These tolerant bacteria were insensitive to 250 nmol of TBTCl per disc, and all were Vibrio species. Total counts of viable bacteria did not decrease upon storage of the TBTCl-treated seawater, indicating that enrichment of tolerant strains took place. Addition of CdSO4 to seawater resulted in the occurrence of TBTCl-tolerant bacteria as well as Cd-tolerant bacteria, suggesting some correlation of Cd tolerance and TBTCl tolerance.

Cadmium↗

Antifungal activity of n-tributyltin acetate against some common yam rot fungi.

The antifungal activity of n-tributyltin acetate (TBTA) was examined in relation to combating yam rot disease. TBTA exhibited a significant effect in vitro and in vivo on four yam rot fungal isolates tested. However, the in vitro toxicity of TBTA was drastically reduced when 2.5% Tween 80 was the solvent instead of 25% acetone, as indicated by the MICs of 156.0 and 5.0 micrograms/ml, respectively.

Antifungal Agents↗

Magnification of tributyl tin toxicity to oyster larvae by bioconcentration in biofilms of Shewanella colwelliana.

The toxic effects of dissolved versus bioconcentrated tributyl tin (TBT) on oyster larvae were compared. Water column TBT levels, which had no effect in solution, inhibited natural attachment and metamorphosis of oyster larvae on bottom surfaces due to bioconcentration by biofilms. This mechanism should be considered when evaluating heavy metal toxicity in the environment.

Animals↗

Effect of bis (tributyl tin) oxide on permeability of the blood-brain barrier: a transient increase.

OBJECTIVES: To study the effect of bis (tributyl tin) oxide (TBTO) on permeability of the blood-brain barrier. METHODS: Electron microscopy and an x ray microanalyser with lanthanum chloride as a tracer were used, and blood tin concentrations were determined with an atomic absorption spectrophotometer. Adult male wistar rats received 0.05 ml/kg body weight of TBTO orally. RESULTS: A transient increase in paracellular permeability at the blood-brain barrier was found 2 h after the dose of TBTO. Electron dense lanthanum deposits penetrated tight junctions of the endothelia and permeated the subendothelial space. The x ray microprobe data showed an accumulation of TBTO at the tight junctions at 2 h. Leakage of tracer did not occur at 4 h, but oedematous changes in the surrounding glial cells were prominent between 4 and 8 h and had almost returned to normal by 24 h. By atomic absorption analysis, it was seen that blood tin concentrations rapidly increased at 1 h and rose to a maximum peak at 8 h, then gradually decreased to reach zero at 24 h. CONCLUSIONS: Accumulated TBTO at tight junctions could have caused the temporary replacement of calcium ion by tin, which induces a transient increase in paracellular permeability throughout the blood-brain barrier.

Animals↗

Evidence for two distinct chloride uniport pathways in brown adipose tissue mitochondria.

Chloride permeability of the inner membrane of brown adipose tissue mitochondria was analyzed by monitoring mitochondrial swelling in KCl salts in the presence of K+ ionophores. The results indicate that the high anion conductance observed in these mitochondria is due to the presence of two separate pathways: 1) a Cl-conducting pathway that is inhibited by guanosine 5'-diphosphate (GDP) but neither by N,N'-dicyclohexylcarbodiimide (DCCD) nor by amphiphilic amines and that is found uniquely in brown adipose tissue mitochondria and 2) an inner membrane anion uniport channel that is inhibited both by DCCD and by amphiphilic amines but not by GDP and that is opened either by depletion of matrix Mg2+ or by alkalinization of the matrix.

Adipose Tissue, Brown↗

Stimulus-secretion coupling in beta-cells: modulation by pH.

We have examined the influence of changes in pH on the oscillatory pattern of electrical activity (EA) in the beta-cell by altering medium pH (pHo) and using permeable weak buffers to alter intracellular pH (pHi). A decrease in pH in the presence of glucose elicited depolarization to the active phase and constant spike activity, whereas an increase in pH elicited a decrease in spike activity or silent hyperpolarization. On inhibition of HCO3:Cl antiport by addition of DIDS (4,4'-diisothiocyano-2,2'-stilbene disulfonic acid), probenecid, or withdrawal of medium HCO-3, there was an increase in the duration of the active phase. A similar result was obtained on the inhibition of Na:H antiport by the addition of amiloride or the reduction of medium [Na+]. The influence of H+ and glucose has been proposed to decrease K+ permeability (PK). However, the influence of pH on 86Rb+ efflux was most effective at subthreshold or 4.2 mM glucose; only a moderate decrease in PK occurred at 8.3 mM glucose, and no effect was obtained at 16.7 mM glucose. Alteration of pHi, and not pHo, induces similar effects on glucose-induced electrical and secretory events. There is a clear dissociation between the influence of inhibitors of the Na:H and HCO3:Cl antiporters on the electrical and secretory events. DIDS and amiloride increased glucose-induced EA, but markedly inhibited the secretory response to glucose. It is evident that pH modulates the electrical events and cationic fluxes and ultimately influences the transduction of information to the mechanisms controlling the secretory process in the beta-cell.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

Na+-H+ and Cl(-)-OH-(HCO3-) exchange in gastric glands.

The pH-sensitive, fluorescent, cytoplasmic-trapped dye 2,7-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) has been used to measure intracellular (pHi) and pH electrode to measure extracellular pH (pHo) in suspensions of gastric glands isolated from rabbit stomachs. The fluorescence of BCECF-loaded glands was calibrated in terms of pHi by equilibrating pHo and pHi using ionophores or digitonin and titrating pHo to different values. An APPENDIX is included that covers details of dye calibration and interpretation of fluorescence signals. Glands incubated in NaCl Ringer solution had pHi 7.11. Na+-free Ringer solution caused pHi to decrease reversibly to 6.80. Na+-dependent alkalinization of pHi followed a similar time course to the acidification of pHo. These changes were blocked by 1 mM amiloride. When gland cells were acidified (using two different techniques) realkalinization was completely Na+ dependent but was independent of the presence of Cl-; also, neither high extracellular K+ concentration ([K+]o) nor high [K+]o plus 10(-5) M valinomycin affected the rates of Na+-dependent alkalinization. A neutral Na+-H+ exchanger was implicated. Glands also exhibited Cl(-)-dependent changes of pHi that were blocked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (2 X 10(-4) M). A Cl(-)-OH-(HCO3-) exchanger was indicated. Other studies showed that intracellular buffering capacity was approximately 45 mM (pH-1) and that the apparent proton conductance of gland cell membranes was small.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

Various indices of brain metabolism and activity in a model of chronic neurological dysfunction: triethyl tin intoxication in the rat.

A number of pathological agents of interest in the therapy of cerebrovascular disease can retard the development of the neurologic deficit induced by triethyl tin. Locomotor activity was decreased at a time when no evidence of neurologic deficit could be detected. Conduction velocity in the peripheral as well as assessed from measurement of cerebral blood flow, local cerebral glucose utilization, brain water and electrolyte content as well as neuropathology were measured before and frank deficit could be clinically detected.

Animals↗

Effects of captopril on locomotor activity, passive avoidance behaviour and spatial memory tasks in the trimethyltin-treated rat.

The potential neuroprotective/cognitive enhancing actions of captopril were investigated in the trimethyltin (TMT)-induced neurotoxicity rat model. Acute exposure to TMT produces alterations in locomotor activity, passive avoidance behaviour and spatial memory tasks. Captopril treatment given in combination with the single acute injection of TMT reversed the deficits in spatial memory tasks in 8 out of 25 trials. While post-treatment of TMT-treated rats with captopril brought about a significant improvement in 3 out of 25 trials, pre-treatment of rats for 3 weeks with captopril did not reverse the behavioural deficits produced by TMT in the Morris maze test. Captopril treatment did not block the characteristic hyperactivity or the deficits in passive avoidance behaviour of TMT-treated animals.

Animals↗

Alterations in behavior, brain electrical activity, cerebral blood flow, and intracranial pressure produced by triethyl tin sulfate induced cerebral edema.

The interrelationships between cerebral edema, intracranial pressure (ICP), and cerebral blood flow (CBF) were studied in acute and chronic triethyl tin sulfate treated rats. Prior to pentobarbital anesthesia behavioral observations were made. ICP and regional CBF were measured under steady state conditions and brain water content was determined by vacuum drying of the right cerebral hemisphere. Control and chronic animals were neurologically normal. There were two distinct acute groups: (1) acute low pressure (ALP) animals - alert but tetraperetic, and (2) acute high pressure (AHP) animals - deeply stuporous, with minimal pain response and gross EEG slowing. ICP was significantly elevated only in AHP animals. Hemispheric CBF was significantly reduced in AHP and chronic animals. The interaction of increased pressure and edema (AHP) produced the greatest decrease in CBF, although deep white flows were significantly affected in all experimental groups. Chronic animals had significantly lower flow in four of seven regions compared to ALP animals despite no significant difference in ICP. Water content was significantly increased in all experimental groups with the greatest increase in the chronic animals. In the absence of any significant increase in ICP, cerebral edema appears to cause a significant reduction in cerebral blood flow and this reduction corresponds with the magnitude and location of the edema.

Acute Disease↗

Quantitative assessment of trimethyltin induced pathology of the hippocampus.

The pathology induced by trimethyltin in the hippocampus was investigated using a detailed morphometric model. Male Long-Evans rats were dosed with 3 mg/kg trimethyltin chloride (TMT) for three consecutive days and sacrificed at subsequent interim period. Total brain volume was not significantly affected; hippocampus volume decreased within 4 days after completion of dose. Pyramidal cells were more sensitive to the toxic effects of TMT than granule cells, in addition, dorsal pyramidal cells appeared to be more sensitive than ventral pyramidal cells. The dorsal CA4 region appeared to be the most susceptible to cell loss, although the dorsal CA1 region also exhibited significant reductions. The most dramatic reduction in cell numbers occurred between 14 and 28 days post-dose. Cell loss within the CA3c and CA4 but not the CA1 region was preceded by decreased nuclear volume. In addition cellular loss within the dorsal CA1 region appeared to be most pronounced within a well defined rectangular patch of cells immediately adjacent to the CA3-CA1 junction. The data further suggest that TMT is a potent toxicant to the hippocampus. This toxicity is delayed, and selectively affects well defined groups of cells within the structure. Additionally, differences in nuclear pathology suggest that more than one mechanism may be involved in the destruction of these target cell populations.

Animals↗